Washington General Knowledge CDL Practice Test

This is a free 20-question practice test for the General Knowledge portion of the Washington Commercial Driver's License knowledge exam. Questions are pulled from a pool of 97 drawn from the AAMVA CDL Manual, which is the source document the Washington State Department of Licensing uses to write its actual exam.

How it works: Click an answer. The correct choice highlights in green, and you'll see a short explanation. Aim for 85% or better before you sit for the real test in Washington.

Question 1 of 20

A driver-side skid can cause a tractor-trailer to:

Drift gently
Jackknife
Improve steering
Over-correct only the trailer

Correct. When the drive wheels lose traction and the trailer continues forward, the tractor pivots and the rig jackknifes.

Question 2 of 20

Which of the following is the best way to prevent a fire in your vehicle?

Carry extra fuel
Smoke only with the windows open
Inspect the vehicle, watch the gauges, and use safe driving practices
Run the engine hot to burn off carbon

Correct. Most fires are preventable through inspection (electrical, fuel-system, tire) and watching gauges, plus prohibiting smoking near fuel and observing safe loading/refueling rules.

Question 3 of 20

Which of these is a major cause of crashes in heavy vehicles?

Driver fatigue
Heavy traffic
Following too closely
All of the above

Correct. Fatigue, heavy traffic, and following too closely are all leading factors in commercial vehicle crashes.

Question 4 of 20

You should back from the driver's side rather than the passenger's side when possible because:

You can see better out of the driver's window
It is required by law
Trailers track that direction
Mirrors only work on that side

Correct. Driver-side ("sight side") backing gives the driver direct visual feedback through the open window in addition to mirror checks.

Question 5 of 20

When should you use your high beams?

Whenever it is dark
When other drivers are within 500 feet ahead
When other drivers are not within 500 feet of you and you are not following another vehicle within 500 feet
In fog

Correct. Federal and state law requires you to dim high beams when within 500 feet of an oncoming vehicle, or when following within 500 feet of another vehicle.

Question 6 of 20

Stopping distance increases significantly when:

Brakes are wet
Tires are worn
You are heavily loaded
All of the above

Correct. Wet brakes, worn tires, heavy load, and slick pavement all extend stopping distance. Plan ahead and follow at greater intervals.

Question 7 of 20

When approaching a downgrade, you should select:

A higher gear than you would for an upgrade
A lower gear before starting down, never after
Neutral, and let gravity slow you
Whatever gear you are in

Correct. Select your gear before the downgrade — modern transmissions can be hard or impossible to shift into a lower gear once you are descending and engine RPM has dropped.

Question 8 of 20

Doubling your speed roughly:

Doubles your stopping distance
Triples your stopping distance
Quadruples your stopping distance
Has no effect on stopping distance

Correct. Braking distance is proportional to the square of speed. Doubling speed roughly quadruples braking distance.

Question 9 of 20

Which of the following can cause the wheels of your vehicle to skid on a curve?

Driving below the posted speed limit
Driving too fast for the curve
Slowing down before entering the curve
Driving with a light load

Correct. Posted curve advisory speeds assume cars; a heavy commercial vehicle with a high center of gravity may roll over or skid even at the posted speed. Slow before the curve, accelerate gently through it.

Question 10 of 20

What does it mean when a driver is "hydroplaning"?

The truck is overheating
The tires lose contact with the road and ride on a film of water
The brakes have failed
The driver is dehydrated

Correct. Hydroplaning means tires have lost contact with the pavement and are riding on standing water. Steering and braking become ineffective.

Question 11 of 20

You are driving a 60-foot tractor-trailer at 55 mph. The minimum following distance you should maintain is:

4 seconds
5 seconds
6 seconds
7 seconds

Correct. Above 40 mph, add one extra second to the per-10-foot rule. A 60-foot vehicle = 6 seconds + 1 = 7 seconds at 55 mph.

Question 12 of 20

What is the minimum amount of tread depth required on tires other than front (steering) tires?

1/32 inch
2/32 inch
4/32 inch
5/32 inch

Correct. Non-steer tires must have at least 2/32-inch tread depth in every major groove.

Question 13 of 20

What is the only effective way to remove alcohol from the body?

Drinking coffee
Cold showers
Eating a heavy meal
Time

Correct. Only time eliminates alcohol from the body — at roughly one drink per hour. Coffee, food, and showers do not speed up the process.

Question 14 of 20

If your vehicle hydroplanes, what should you do?

Brake hard immediately
Steer sharply to recover
Release the accelerator and push in the clutch
Accelerate to push through

Correct. Release the accelerator and push in the clutch. Do not brake or steer hard until the tires regain contact.

Question 15 of 20

Which of these is the best advice for staying alert on a long trip?

Drink coffee
Take cold pills
Get enough sleep before the trip and take rest breaks
Open the window

Correct. Adequate sleep before driving and scheduled rest breaks are the only reliable strategies. Coffee and cold air mask fatigue but do not eliminate it.

Question 16 of 20

Which of these vehicles is most likely to have to stop at a railroad crossing?

A school bus or a placarded hazmat vehicle
A pickup truck
A motorcycle
A passenger car

Correct. Buses, school buses, and placarded hazmat vehicles must stop at every railroad crossing 15 to 50 feet from the nearest rail.

Question 17 of 20

When stopping at the scene of an accident, you should:

Move your vehicle into traffic to make room
Park well off the road, set out warning devices, and offer assistance
Leave the scene immediately
Drive around the accident

Correct. Park clear of the road, activate four-way flashers, set out warning triangles, and assist as you can without putting yourself in danger.

Question 18 of 20

When you arrive at a customer to deliver:

Just open the trailer
Sign in, follow site safety rules (PPE, speed limits, designated routes)
Skip site rules
Park anywhere

Correct. Customer sites have their own safety rules — sign in, wear required PPE, follow speed limits and designated routes.

Question 19 of 20

Most drivers who fall asleep at the wheel:

Are aware they are tired and pull over
Do not realize they are about to fall asleep
Have been drinking
Have been on the road less than an hour

Correct. Most drivers who fall asleep do not realize how drowsy they are. The only fix is to stop and rest before fatigue reaches that point.

Question 20 of 20

When you exit a highway in a heavy commercial vehicle, you should:

Maintain highway speed onto the ramp
Slow down before reaching the ramp curve, since posted advisory speeds assume cars
Speed up to clear the ramp
Brake only at the bottom

Correct. Posted ramp speeds assume passenger cars. A loaded heavy vehicle, especially with high CG, can roll over at the posted speed. Slow before the curve.

About the Washington General Knowledge exam

Most state DMVs administer 50 General Knowledge questions and require 80% (40 correct) to pass. Questions are pulled from a much larger pool, so two applicants taking the test on the same day will see different mixes. The questions on this site are drawn from the AAMVA CDL Manual chapters that every state's exam is built from.

The Washington State Department of Licensing follows the federal CDL standards established by FMCSA. To earn the General Knowledge credential, you must answer at least 80% of the questions correctly. Many candidates score lower the first time because the test pulls from a large pool — refreshing this page will give you a different mix of questions, drawn from the same authoritative source.

Want more practice? Try the full General Knowledge question bank or browse all Washington CDL practice tests.